Programming in D for C++ Programmers

Overview

D is a modern multi-paradigm programming language that emphasizes both productivity and native efficiency. D does not compromise performance while making great strides in productivity and program correctness, which makes it a great choice for C++ programmers.

D also emphasizes modeling power: D allows for the design and implementation of high-level interfaces without compromising performance, allowing unparalleled code reuse in performance-sensitive projects.

D can interface with both C and C++ code, but D sheds the burden of backwards compatibility with C source code, which allows it to make the easy way the *correct* way.

Header files

D has a comprehensive, no-nonsense module system that alleviates the need for header files. Symbols can be forward-referenced freely.

D still supports the equivalent of header files - D interface files - which can be used to interface with C or C++ code, or closed-source D code.

Compile times

D is designed to be fast to compile. Despite having more comprehensive and intuitive metaprogramming features than C++, compilation times tend to be significantly shorter for equivalent programs.

The short compilation time also makes D suitable for writing scripts, executed with rdmd.

Checked memory safety and functional purity

D supports opt-in, transitively-enforced memory safety:

import std.stdio;

void main() @safe // Verified by the compiler to be memory safe
{
	writeln("hello, world");
}

D also supports opt-in functional purity, giving semantic cues to both the programmer and the compiler. Purity makes programs easier to reason about for programmers, and easier to optimize for compilers.

Concurrency

D's memory model is designed to make shared memory explicit, greatly reducing the potential for concurrency bugs:

Immutability

D supports transitive immutable data, enforced by the type system. A variable of immutable type is guaranteed to never change after initialization.

There are also const types, bridging mutable and immutable data into a common supertype, enabling functions to receive both mutable and immutable data.

Metaprogramming

D templates are both more expressive and easier to read and write than C++ templates. static-if enables conditional branching in imperative style, eliminating the need for specialized dummy types.

Ranges vs iterators

D espouses ranges, an evolution of the iterator concept more conducive to component programming:

import std.stdio;
import std.array;
import std.algorithm;

void main()
{
    stdin
    	.byLine(KeepTerminator.yes)
	    .map!(a => a.idup)
	    .array
	    .sort
	    .copy(
	        stdout.lockingTextWriter());
}

Ranges are also more conducive to presenting safe interfaces.

Undefined behaviour

D tastefully reduces the number of undefined behaviours from C++ by defining them out of existence.

Unicode

D and its standard library was designed with Unicode in mind, and supports Unicode on a number of levels:

• D source files are UTF encoded
• The types string, wstring and dstring are UTF-8, UTF-16 and UTF-32 strings respectively